package com.skh.linkedlist;

/**
 * @Author: skh
 * @Date: 2019/6/11 15:38
 * @Description: 21.合并两个有序链表
 */
public class MergeTwoLists {

    /*
    将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 

    示例：
         l1 l1    l2
    输入：1->2->4, 1 ->3->4
         head
    输出：1->1->2->3->4->4
     */

    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

        if (l1 == null) {
            return l2;
        }

        if (l2 == null) {
            return l1;
        }

        if (l1.val < l2.val) {
            l1.next = mergeTwoLists(l1.next, l2);
            return l1;
        }else {
            l2.next = mergeTwoLists(l1, l2.next);
            return l2;
        }

    }

    public ListNode mergeTwoLists1(ListNode l1, ListNode l2) {

        ListNode head = new ListNode(0);

        ListNode cur = head;

        while (l1 != null && l2 != null) {
            if (l1.val < l2.val) {
                cur.next = l1;
                l1 = l1.next;
                cur = cur.next;
            }else {
                cur.next = l2;
                l2 = l2.next;
                cur = cur.next;
            }
        }

        if (l1 == null) {
            cur.next = l2;
        }else {
            cur.next = l1;
        }

        return head.next;
    }
}
